<!-- Licensed under a BSD license. See license.html for license -->
<!DOCTYPE html>
<html>
  <head>
    <meta charset="utf-8">
    <meta name="viewport" content="width=device-width, initial-scale=1.0, user-scalable=yes">
    <title>Three.js - Cameras - Perspective 2 views</title>
    <style>
    html, body {
        margin: 0;
        height: 100%;
    }
    #c {
        width: 100%;
        height: 100%;
        display: block;
    }
    .split {
      position: absolute;
      left: 0;
      top: 0;
      width: 100%;
      height: 100%;
      display: flex;
    }
    .split>div {
      width: 100%;
      height: 100%;
    }
    </style>
  </head>
  <body>
    <canvas id="c"></canvas>
    <div class="split">
       <div id="view1" tabindex="1"></div>
       <div id="view2" tabindex="2"></div>
    </div>
  </body>
<script type="importmap">
{
  "imports": {
    "three": "../../build/three.module.js",
    "three/addons/": "../../examples/jsm/"
  }
}
</script>

<script type="module">
import * as THREE from 'three';
import { OrbitControls } from 'three/addons/controls/OrbitControls.js';
import { GUI } from 'three/addons/libs/lil-gui.module.min.js';

function main() {

	const canvas = document.querySelector( '#c' );
	const view1Elem = document.querySelector( '#view1' );
	const view2Elem = document.querySelector( '#view2' );
	const renderer = new THREE.WebGLRenderer( { antialias: true, canvas } );

	const fov = 45;
	const aspect = 2; // the canvas default
	const near = 5;
	const far = 100;
	const camera = new THREE.PerspectiveCamera( fov, aspect, near, far );
	camera.position.set( 0, 10, 20 );

	const cameraHelper = new THREE.CameraHelper( camera );

	class MinMaxGUIHelper {

		constructor( obj, minProp, maxProp, minDif ) {

			this.obj = obj;
			this.minProp = minProp;
			this.maxProp = maxProp;
			this.minDif = minDif;

		}
		get min() {

			return this.obj[ this.minProp ];

		}
		set min( v ) {

			this.obj[ this.minProp ] = v;
			this.obj[ this.maxProp ] = Math.max( this.obj[ this.maxProp ], v + this.minDif );

		}
		get max() {

			return this.obj[ this.maxProp ];

		}
		set max( v ) {

			this.obj[ this.maxProp ] = v;
			this.min = this.min; // this will call the min setter

		}

	}

	const gui = new GUI();
	gui.add( camera, 'fov', 1, 180 );
	const minMaxGUIHelper = new MinMaxGUIHelper( camera, 'near', 'far', 0.1 );
	gui.add( minMaxGUIHelper, 'min', 0.1, 50, 0.1 ).name( 'near' );
	gui.add( minMaxGUIHelper, 'max', 0.1, 50, 0.1 ).name( 'far' );

	const controls = new OrbitControls( camera, view1Elem );
	controls.target.set( 0, 5, 0 );
	controls.update();

	const camera2 = new THREE.PerspectiveCamera(
		60, // fov
		2, // aspect
		0.1, // near
		500, // far
	);
	camera2.position.set( 40, 10, 30 );
	camera2.lookAt( 0, 5, 0 );

	const controls2 = new OrbitControls( camera2, view2Elem );
	controls2.target.set( 0, 5, 0 );
	controls2.update();

	const scene = new THREE.Scene();
	scene.background = new THREE.Color( 'black' );
	scene.add( cameraHelper );

	{

		const planeSize = 40;

		const loader = new THREE.TextureLoader();
		const texture = loader.load( 'resources/images/checker.png' );
		texture.wrapS = THREE.RepeatWrapping;
		texture.wrapT = THREE.RepeatWrapping;
		texture.magFilter = THREE.NearestFilter;
		texture.colorSpace = THREE.SRGBColorSpace;
		const repeats = planeSize / 2;
		texture.repeat.set( repeats, repeats );

		const planeGeo = new THREE.PlaneGeometry( planeSize, planeSize );
		const planeMat = new THREE.MeshPhongMaterial( {
			map: texture,
			side: THREE.DoubleSide,
		} );
		const mesh = new THREE.Mesh( planeGeo, planeMat );
		mesh.rotation.x = Math.PI * - .5;
		scene.add( mesh );

	}

	{

		const cubeSize = 4;
		const cubeGeo = new THREE.BoxGeometry( cubeSize, cubeSize, cubeSize );
		const cubeMat = new THREE.MeshPhongMaterial( { color: '#8AC' } );
		const mesh = new THREE.Mesh( cubeGeo, cubeMat );
		mesh.position.set( cubeSize + 1, cubeSize / 2, 0 );
		scene.add( mesh );

	}

	{

		const sphereRadius = 3;
		const sphereWidthDivisions = 32;
		const sphereHeightDivisions = 16;
		const sphereGeo = new THREE.SphereGeometry( sphereRadius, sphereWidthDivisions, sphereHeightDivisions );
		const sphereMat = new THREE.MeshPhongMaterial( { color: '#CA8' } );
		const mesh = new THREE.Mesh( sphereGeo, sphereMat );
		mesh.position.set( - sphereRadius - 1, sphereRadius + 2, 0 );
		scene.add( mesh );

	}

	{

		const color = 0xFFFFFF;
		const intensity = 3;
		const light = new THREE.DirectionalLight( color, intensity );
		light.position.set( 0, 10, 0 );
		light.target.position.set( - 5, 0, 0 );
		scene.add( light );
		scene.add( light.target );

	}

	function resizeRendererToDisplaySize( renderer ) {

		const canvas = renderer.domElement;
		const width = canvas.clientWidth;
		const height = canvas.clientHeight;
		const needResize = canvas.width !== width || canvas.height !== height;
		if ( needResize ) {

			renderer.setSize( width, height, false );

		}

		return needResize;

	}

	function setScissorForElement( elem ) {

		const canvasRect = canvas.getBoundingClientRect();
		const elemRect = elem.getBoundingClientRect();

		// compute a canvas relative rectangle
		const right = Math.min( elemRect.right, canvasRect.right ) - canvasRect.left;
		const left = Math.max( 0, elemRect.left - canvasRect.left );
		const bottom = Math.min( elemRect.bottom, canvasRect.bottom ) - canvasRect.top;
		const top = Math.max( 0, elemRect.top - canvasRect.top );

		const width = Math.min( canvasRect.width, right - left );
		const height = Math.min( canvasRect.height, bottom - top );

		// setup the scissor to only render to that part of the canvas
		const positiveYUpBottom = canvasRect.height - bottom;
		renderer.setScissor( left, positiveYUpBottom, width, height );
		renderer.setViewport( left, positiveYUpBottom, width, height );

		// return the aspect
		return width / height;

	}

	function render() {

		resizeRendererToDisplaySize( renderer );

		// turn on the scissor
		renderer.setScissorTest( true );

		// render the original view
		{

			const aspect = setScissorForElement( view1Elem );

			// adjust the camera for this aspect
			camera.aspect = aspect;
			camera.updateProjectionMatrix();
			cameraHelper.update();

			// don't draw the camera helper in the original view
			cameraHelper.visible = false;

			scene.background.set( 0x000000 );

			// render
			renderer.render( scene, camera );

		}

		// render from the 2nd camera
		{

			const aspect = setScissorForElement( view2Elem );

			// adjust the camera for this aspect
			camera2.aspect = aspect;
			camera2.updateProjectionMatrix();

			// draw the camera helper in the 2nd view
			cameraHelper.visible = true;

			scene.background.set( 0x000040 );

			renderer.render( scene, camera2 );

		}

		requestAnimationFrame( render );

	}

	requestAnimationFrame( render );

}

main();
</script>
</html>
